Piano Sonata No.13 in B-flat major, KV 333

There is no doubt that this sonata was first published on 21 April 1784 in Vienna by Christoph Torricella (along with K. 284 and K. 454, as op. 7). The actual date of composition, however, has proved more difficult to determine. Because the manuscript is not written on the type of music paper Mozart is known to have used in Vienna, scholars believed that the piece was composed before Mozart moved to that city. Thus Köchel, in the first edition of his Mozart catalog (1862), gave the hypothetical date 1779, later clarified by Georges de Saint-Foix (1936) to "Salzburg, beginning of January–March 1779." However, Alfred Einstein, in the third edition of the Köchel catalog (1937), said that it was composed in "late summer 1778 in Paris." This date was maintained even until the sixth edition of the Köchel catalog (1964).